Simultaneous intracellular recordings from longitudinal and circular muscle during the peristaltic reflex in guinea-pig distal colon
Article first published online: 5 AUG 2004
The Journal of Physiology
Volume 533, Issue 3, pages 787–799, June 2001
How to Cite
Spencer, N. J. and Smith, T. K. (2001), Simultaneous intracellular recordings from longitudinal and circular muscle during the peristaltic reflex in guinea-pig distal colon. The Journal of Physiology, 533: 787–799. doi: 10.1111/j.1469-7793.2001.00787.x
- Issue published online: 5 AUG 2004
- Article first published online: 5 AUG 2004
- (Received 30 October 2000; accepted after revision 5 February 2001)
- 1Simultaneous intracellular recordings were made from longitudinal muscle (LM) and circular muscle (CM) cells of guinea-pig distal colon during the peristaltic reflex.
- 2Spontaneous rhythmical depolarizations with superimposed action potentials (mean amplitude: 19 ± 2 mV) were regularly recorded from the LM (mean interval: 7 ± 1 s). In contrast, in the CM layer, spontaneous action potentials occurred with an irregular frequency. Although spontaneous action potentials in LM were rarely correlated in time with those in CM, spontaneous inhibitory junction potentials (sIJPs) were found to occur synchronously in both muscles (5 out of 27 animals; 19 %).
- 3Graded inflation of an intra-luminal balloon or mucosal stimulation oral to the recording electrodes elicited gradeable compound IJPs synchronously in both LM (mean amplitude: 6 ± 1 mV) and CM (mean amplitude: 9 ± 1 mV) (descending inhibitory reflex). Evoked IJPs were often followed by action potentials in both muscle layers.
- 4Mucosal stimuli applied anal to the recording electrodes elicited compound excitatory junction potentials (EJPs) synchronously in both muscles layers that were often associated with the generation of action potentials. In the LM, evoked EJP amplitudes ranged from 3 mV (subthreshold) to 31 mV (including the action potential) and in the CM from 4 mV (subthreshold) to 44 mV (including the action potential).
- 5Apamin (500 nM) reduced the evoked IJP in the CM by 55 % (from 11 ± 2 to 5 ± 1 mV), but caused no significant reduction in the LM layer (from 8 ± 1 to 6 ± 1 mV). Apamin-resistant IJPs in both muscle layers were likely to be due to nitric oxide, since they were abolished by L-NA (100 μM).
- 6Atropine (1 μM) abolished the ascending excitatory reflex in both muscles.
- 7Injection of neurobiotin into the LM and CM confirmed that simultaneous intracellular recordings were made from different muscle layers.
- 8In conclusion, during the peristaltic reflex, the LM and CM layers receive synchronous inhibitory neuromuscular inputs during descending inhibition and synchronous excitatory neuromuscular inputs during ascending excitation. No evidence was found to support reciprocal innervation.